In general, while cyclic olefin copolymer is being prepared, gel formation is observed during or after the reaction.
The gel formed thereby increases the solution viscosity of a polymer and might inhibit the flow of a reactant or a reaction product by being accumulated on the wall or pipe line of a reactor, causing a serious problem during commercial processes. Also the solubility of a polymer containing the gel at more than the allowable amount decreases in an organic solvent, and processing performance of the polymer might be reduced because it cannot be melted evenly by heat. In the case when a polymer contains the gel at more than the allowable amount after polymerization, the efficiency of the following hydrogenation drops significantly, and thus the double bonds remaining in the polymer chain are degraded by foreign factors such as UV and heat, thereby degrading the properties of a product. Therefore, the formation of gel is a crucial problematic factor for cyclic olefin copolymer production by ROMP.
Copolymer of ethylene, propylene and cyclic olefin compound can have excellent properties, particularly transparency and thermal resistance, which is something that the conventional polyethylene or polypropylene cannot provide, with the insertion of an integrate cyclic structure in the backbone of the copolymer. Thus, cyclic olefin polymer or copolymer, as an optical material having excellent transparency and low-hygroscopy, can be used in various fields including DVDs, CDs, lenses and optical fiber etc, instead of polycarbonate (PC) or polymethylmethacrylate (PMMA) resin which have been used as information recording materials.
Recently, various norbornene derivatives having alkyl and polar functional groups have been used for the production of cyclic olefin polymer, and such norbornene derivatives can be applied not only to the production of copolymers but also to the production of single polymers.
Some of the advanced cyclic olefin copolymer manufacturing companies are underway with the development of the advanced next generation materials having super properties, particularly excellent thermal-, mechanical-, and optical properties, which is the ultimate goal that the conventional polyolefin cannot reach, by copolymerization of ethylene and styrene, cyclic olefin and methylmethacrylate. Especially, the copolymer produced by the copolymerization of cyclic olefin compound and ethylene has excellent optical and thermal properties, making the copolymer an excellent candidate for the next generation material for information recording such as CD and DVD.
Norbornene polymer can not only replace polycarbonate but also reduce the gap between CD tracks, suggesting that it enables high integration so as to be used for the next generation DVD (HD-DVD). In addition, the polymer has a great potential in the application of lenses for camcorders or auto-cameras, etc. owing to its excellent optical properties, dimensional stability, moisture resistance and low density.
Polymerization catalysts used for the production of a polymer using cyclic olefin compound are largely divided as follows; ROMP (Ring Opening Metathesis Polymerization) catalysts; addition polymerization catalysts; cationic catalysts; and radical initiators.
ROMP catalysts, addition polymerization catalysts and cationic catalysts can be commonly used for the production of cyclic olefin copolymer having excellent transparency. In the case of using ROMP catalysts, it is required to saturate the double bond of the polymerized polymer by hydrogenation, which is a disadvantage, but it is superior to other catalysts in the polymerization of monomers harboring hetero atoms. In the case of using addition polymerization catalysts, it is possible to produce the final polymer product right after the polymerization, but it has a low rate of polymerization of monomers harboring hetero atoms.
Major metal components of ROMP catalyst are Mo, W, Ru and Re, and the activity of the catalyst can be regulated by modifying the ligand arranged near the metals or applying different cocatalysts and additives.
Major metal components composing addition polymerization catalyst are Ti, Zr, Cr, Co, Ni and Pd. Among these metals, Ni and Pd are the most representative metal catalysts used for the production of cyclic olefin copolymer.
The advantages of the cyclic olefin copolymer are low density, high transparency, low hygroscopy and heat-resistance, which enable the replacement of the conventional glass, acrylic polymer, polycarbonate and polyvinylidene chloride (PVDC).
U.S. Pat. Nos. 4,002,815 and 4,069,376 describe a method to regulate the amount of gel produced during ROMP of cyclic olefin compound, in which non-cyclic non-conjugated olefin compound, having a least one hydrogen atom on each double-bonded carbon atom, were mixed with W salt compound and a complex prepared by mixing AlR2I, AlRI2 or AlR3 and I2 was used as a polymerization catalyst to control gel production during the polymerization. However, the polymerization yield was comparatively low (less than 70%) in the former and the polymerization yield was between 6-100% in the latter, indicating that the polymerization activity varies with the polymerization conditions.
U.S. Pat. Nos. 6,020,443 and 5,939,504 describe another method to regulate gel production by regulating the polymerization reaction speed using Lewis base compound, in which such compounds as phosphine, phosphite, ether, amine, amide sulfoxide, nitrile or furan were used. However, using a reaction speed regulator makes the reaction processes more complicated and might reduce the polymerization yield in some cases.
In the meantime, U.S. Pat. No. 4,400,340 describes a method of preparing cyclic olefin copolymer using RIM (Reaction Injection Molding Process). According to the description, cylcic olefin copolymer is produced using a complex prepared by adding ether, ester, or keytone compound, as a reaction speed regulator, to the mixture of W salt compound and dialkylaluminum halide or alkylaluminum dihalide compound. Similarly, U.S. Pat. No. 4,882,401 describes a method of preparing cyclic olefin copolymer by using a complex prepared by adding ether, phosphine, or phosphite compound as a reaction speed regulator and dialkylzinc or alkylzinc halide compound as a catalyst activator to W salt compound or Mo salt compound. However, this method also has a problem of creating complicated processes resulting from the addition of a catalyst activator and a reaction speed regulator.
U.S. Pat. No. 3,997,471 describes a method of preparing cyclic polymer, in which a complex prepared by adding an alcohol compound harboring a nitrile group or a halogen element, as a reaction speed regulator, to the mixture of W salt compound and dialkylaluminum halide is used as a catalyst. However, the polymerization yield according to this method is less than 80%. Similarly, U.S. Pat. No. 6,511,756 describes a method of preparing cyclic olefin polymer using a complex prepared by adding a compound harboring a nitrile group, ketone group, ether group or ester group, as a reaction speed regulator, to the mixture of W salt or Mo salt compound and an organoaluminum compound. However, this method also has a problem of creating complicated processes resulting from the addition of a reaction regulator.
Further, U.S. Pat. No. 4,060,468 describes a method of preparing catalytic active species by irradiating UV onto a complex prepared by adding a phenol derivative to W salt or Mo salt compound. But, this unique method of preparing catalytic active species seems to have a limitation when applied to mass-production.
In the meantime, U.S. Pat. No. 5,840,820 describes a method of preparing cyclic olefin polymer, in which Ru carbene complex compound is used as a single catalyst, or a complex preparing by adding organoaluminum halide compound or organic alkyl tin compound by W salt complex compound is used as a catalyst, and in that case CO2 is used as a polymerization solvent. But the polymerization yield according to this method is less than 80% even though the polymerization reaction is continued for a long time (more than 10 hours ) under high pressure (over 1000 psi).
U.S. Pat. No. 6,433,113 describes a method of preparing cyclic olefin polymer by adding α-olefin as a chain transfer agent to the mixture of Mo salt compound and organoaluminum compound. According to this method, the polymerization yield varies significantly with the polymerization conditions (polymerization yield=10˜100%).
On the other hand, instead of organoaluminum halide compound, which has been used as one of the major components forming catalytic systems for the production of cyclic olefin polymer, organic alkyl tin compound has been tested. For example, U.S. Pat. No. 4,810,762 describes a method of preparing cyclic olefin polymer by using a complex, as a catalyst, prepared by adding R3SnH or Ph3SnH to W salt compound with the substitution of phenol derivatives. U.S. Pat. No. 5,081,208 describes a preparing method of cyclic olefin polymer by using a complex, as a catalyst, prepared by adding R3SnH compound to the mixture of W salt compound and phenol compound. However, the above two methods have the problem of using an Sn compound, which is known as a harmful substance.